For two decades, anthropologists have been aware that the experience and symptoms of menopause (i.e., hot flashes, night sweats) may not be universal. Several researchers have hypothesized that dietary factors such as phytoestrogens (plant estrogenic chemicals) in soy, which is consumed in great quantities by the Japanese, may play a role in their lower rate of menopausal symptoms. This dissertation project will test a biocultural, reproductive ecology model of whether and how soy consumption affects the menopausal transition (konenki) in Japan. Specifically, we hypothesize that: (1) Women with higher phytoestrogen exposure/intake will have less frequent or severe midlife symptoms; and (2) Variance in gonadotropins (FSH and LH) will be negatively correlated with phytoestrogen exposure. Two populations of Japanese women, aged 45-55, from the Tohoku and Kinki regions of Japan (which have the highest and lowest soy consumption respectively, providing a natural experiment in phytoestrogen exposure) will be sampled longitudinally for levels of E2, FSH, LH, SHBG, and the phoytoestrogens genistein and diadzein. This study will characterize the menopausal transition in Japan from multiple perspectives: (1) endocrinological/physiological; (2) ecological (diet), and (3) experimental. By combining new assays for measurement of phytoestrogens with our well-validated finger prick blood spot methods, this project will provide a biocultural characterization of menopause in Japan. These data are sorely needed to model cross-cultural variation at the end of the reproductive lifespan, and the influence of the environment on endocrinology and experience over the menopausal transition.